1. Field of the Invention
This invention relates to an image-forming method for forming an image on a transparent film used as a transparent recording medium through which the image is projected on a screen by an overhead projector (OHP), and an image-forming transparent film used in such a method; the film being usable in electrophotographic apparatus, electrostatic recording apparatus and so forth. More particularly, it relates to an image-forming method of forming an image on a transparent film having an opaque zone that serves as a marking for optically detecting the position of the transparent film in an image-forming apparatus or serves as a marking for optically detecting the state of transport of the transparent film in the image-forming apparatus, and an image-forming transparent film used in such a method.
2. Related Background Art
Forming images on OHP films in recording apparatuses such as electrophotographic, ink-jet or thermal transfer recording apparatuses is conventionally in wide use. Its importance is considered to increase in the future.
As OHP films, resin films such as polyethylene terephthalate film with a thickness of about 100 to 150 xcexcm are commonly often used, and a desired image-recording layer (image-receiving layer) is optionally provided thereon so that the fixability, maintenance or resolution of images can also be improved.
It is also common to provide a transparent film with an opaque mark beforehand on its surface for the purpose of its use in common with opaque recording sheets in one image-forming apparatus, and to sense this opaque mark by an optical sensor of the image-forming apparatus to detect the position of the transparent film. However, such an opaque mark for detecting the position of the transparent film remains also after image formation to bring about the problems that it remains as an image extraneous to the recorded image to make OHP-projected images very unsightly and also make images illegible when it overlaps with the recorded image.
As a countermeasure therefor, it is proposed in, e.g., Japanese Patent Applications Laid-open No. 57-76554 and No. 58-90647 to provide a transparent film with a readily peelable opaque member at an edge on its side opposite to the side on which images are transferred (i.e., image transfer side). The transparent film proposed therein enables optical detection with the readily peelable opaque member provided at an edge on the side opposite to the image transfer side. When used in OHP, the opaque member is peeled, thus the whole film can effectively be used, as so stated.
In such a method, however, there is a possibility that the opaque member peels off midway in the course the transparent film is transported through inside the image-forming apparatus. This may cause trouble of the image-forming apparatus. Also, users must pay attention also when the opaque member is peeled, and there arise problems that the film may break and scratches and adhesive paste used may remain on the film.
In Japanese Patent Application Laid-open No. 3-170944, also proposed is a transparent film, an opaque member provided on the surface of which turns transparent upon heating to become invisible. The transparent film proposed therein has advantages that the above peel-off in the image-forming apparatus and users"" attention may no longer be of any concern. It, however, has been found that this opaque member causes a problem that, when formed simply, it does not become sufficiently invisible after only one rotation of a fixing roller. This is because the heat of the fixing roller is partly lost through the transfer material and the fixing roller from which the heat has partly been lost supplies that heat to the transparent film.
An object of the present invention is to solve the above problems to provide an image-forming method that can form a high-grade recorded image such that any unwanted opaque matter other than images formed is present on the transparent film on which the images have been formed, and an image-forming transparent film used in such a method.
Another object of the present invention is to provide an image-forming method that can form a high-grade transparent recorded image such that, even though an opaque zone is provided in a transparent film at its position coming after one rotation of a fixing roller, any unwanted opaque matter other than images formed is not present on the transparent film after fixing, and an image-forming transparent film used in such a method.
The present invention provides an image-forming method comprising forming an image on a transparent film for an overhead projector, followed by fixing in a fixing step to form a recorded image, wherein
the transparent film is provided on its surface with an opaque sensing mark layer capable of turning transparent upon heating with a fixing roller and an opaque mark layer capable of turning transparent upon that heating;
the opaque mark layer being capable of more readily turning transparent upon heating than the opaque sensing mark layer and being formed on the side upstream in the film transport direction from the position coming after substantially one rotation of the fixing roller, measured from an end of the transparent film in its transport direction; and
the opaque sensing mark layer being formed on the downstream side of the opaque mark layer.
The present invention also provides an image-forming transparent film having on its surface an opaque sensing mark layer capable of turning transparent upon heating and an opaque mark layer capable of turning transparent upon that heating,
the opaque mark layer being formed on the side upstream to the opaque sensing mark layer in the film transport direction and being so formed as to be capable of more readily turning transparent upon heating than said opaque sensing mark layer.
In the image-forming method of the present invention, in order to solve the problem that the opaque zone provided on the surface of the transparent film does not become sufficiently transparent at its part coming after one rotation of the fixing roller, an opaque sensing mark layer is formed in a film area extending between the part with which the fixing roller begins to come into contact and the part where it has substantially rotated once, and an opaque mark layer is formed on the upstream side of the opaque sensing mark layer. The opaque mark layer is a layer capable of turning transparent upon heating at a temperature lower than the temperature at which the opaque sensing mark layer turns transparent.
The opaque mark layer may have an optical function as a sensing mark. It may also be utilized as an indication mark that shows the transport direction of the transparent film, and an indication mark for distinguishing between the surface and the back of the transparent film.
Thus, in the transparent film according to the present invention, the opaque sensing mark layer is formed on the downstream or forward side in the transport direction, and the opaque mark layer on the upstream or backward side.